<template>
  <view class="content">
    <scroll-view
      scroll-y
      class="left-aside"
    >
      <view
        v-for="item in flist"
        :key="item.id"
        class="f-item b-b"
        :class="{active: item.id === currentId}"
        @click="tabtap(item)"
      >
        {{ item.name }}
      </view>
    </scroll-view>
    <scroll-view
      scroll-with-animation
      scroll-y
      class="right-aside"
      :scroll-top="tabScrollTop"
      @scroll="asideScroll"
    >
      <view
        v-for="item in slist"
        :id="'main-'+item.id"
        :key="item.id"
        class="s-list"
      >
        <text class="s-item">
          {{ item.name }}
        </text>
        <view class="t-list">
          <block v-for="titem in tlist" :key="titem.id">
            <view
              v-if="titem.pid === item.id"
              class="t-item"
              @click="navToList(item.id, titem.id)"
            >
              <image :src="titem.picture" />
              <text>{{ titem.name }}</text>
            </view>
          </block>
        </view>
      </view>
    </scroll-view>
  </view>
</template>

<script>
export default {
  data() {
    return {
      sizeCalcState: false,
      tabScrollTop: 0,
      currentId: 1,
      flist: [],
      slist: [],
      tlist: [],
    }
  },
  onLoad(){
    this.loadData()
  },
  methods: {
    async loadData(){
      const list = await this.$api.json('cateList')
      list.forEach(item => {
        if(!item.pid){
          this.flist.push(item) // pid为父级id, 没有pid或者pid=0是一级分类
        }else if(!item.picture){
          this.slist.push(item) // 没有图的是2级分类
        }else{
          this.tlist.push(item) // 3级分类
        }
      }) 
    },
    // 一级分类点击
    tabtap(item){
      if(!this.sizeCalcState){
        this.calcSize()
      }
				
      this.currentId = item.id
      const index = this.slist.findIndex(sitem => sitem.pid === item.id)
      this.tabScrollTop = this.slist[index].top
    },
    // 右侧栏滚动
    asideScroll(e){
      if(!this.sizeCalcState){
        this.calcSize()
      }
      const scrollTop = e.detail.scrollTop
      const tabs = this.slist.filter(item => item.top <= scrollTop).reverse()
      if(tabs.length > 0){
        this.currentId = tabs[0].pid
      }
    },
    // 计算右侧栏每个tab的高度等信息
    calcSize(){
      let h = 0
      this.slist.forEach(item => {
        const view = uni.createSelectorQuery().select('#main-' + item.id)
        view.fields({
          size: true
        }, data => {
          item.top = h
          h += data.height
          item.bottom = h
        }).exec()
      })
      this.sizeCalcState = true
    },
    navToList(sid, tid){
      uni.navigateTo({
        url: `/pages/product/product?fid=${this.currentId}&sid=${sid}&tid=${tid}`
      })
    }
  }
}
</script>

<style lang='scss'>
	page,
	.content {
		height: 100%;
		background-color: #f8f8f8;
	}

	.content {
		display: flex;
	}
	.left-aside {
		flex-shrink: 0;
		width: 200rpx;
		height: 100%;
		background-color: #fff;
	}
	.f-item {
		display: flex;
		align-items: center;
		justify-content: center;
		width: 100%;
		height: 100rpx;
		font-size: 28rpx;
		color: $font-color-base;
		position: relative;
		&.active{
			color: $base-color;
			background: #f8f8f8;
			&:before{
				content: '';
				position: absolute;
				left: 0;
				top: 50%;
				transform: translateY(-50%);
				height: 36rpx;
				width: 8rpx;
				background-color: $base-color;
				border-radius: 0 4px 4px 0;
				opacity: .8;
			}
		}
	}

	.right-aside{
		flex: 1;
		overflow: hidden;
		padding-left: 20rpx;
	}
	.s-item{
		display: flex;
		align-items: center;
		height: 70rpx;
		padding-top: 8rpx;
		font-size: 28rpx;
		color: $font-color-dark;
	}
	.t-list{
		display: flex;
		flex-wrap: wrap;
		width: 100%;
		background: #fff;
		padding-top: 12rpx;
		&:after{
			content: '';
			flex: 99;
			height: 0;
		}
	}
	.t-item{
		flex-shrink: 0;
		display: flex;
		justify-content: center;
		align-items: center;
		flex-direction: column;
		width: 176rpx;
		font-size: 26rpx;
		color: #666;
		padding-bottom: 20rpx;
		
		image{
			width: 140rpx;
			height: 140rpx;
		}
	}
</style>
